1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, apparatus, and products for memory downsizing in a computer memory subsystem.
2. Description of Related Art
The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely complicated devices. Today's computers are much more sophisticated than early systems such as the EDVAC. Computer systems typically include a combination of hardware and software components, application programs, operating systems, processors, buses, memory, input/output devices, and so on. As advances in semiconductor processing and computer architecture push the performance of the computer higher and higher, more sophisticated computer software has evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
Advances in computer systems are largely dependent upon advances in computer memory. In computer systems today, for example, computer memory subsystems often include many different modules of memory, multiple Dual In-line Memory Modules (‘DIMMs’) for example, in many different configurations. In some computer memory subsystems DIMMs are configured in channels. In current computer systems, upon startup of the computer system, a firmware module such as BIOS or EFI runs a memory initialization test to determine if the DIMMs in each channel are defective. If the firmware determines that a DIMM is defective, in current art, the firmware proceeds to downsize memory by disabling, that is, de-allocating or mapping out of available system memory, all DIMMs in the same channel located behind the defective DIMM—whether defective of not. A DIMM is said to be ‘behind’ another DIMM in a channel when the DIMM is located physically further away from a memory controller in the data path than the other DIMM. In some cases according to memory downsizing methods of the current art, all DIMMs in a channel may be disabled, even all DIMMs in the computer system, even if many of the DIMMs are non-defective.